Effect of Stove Types on In-kitchen Air Quality: Case Study at Way Isem Village, Lampung Province, Indonesia

• *Corresponding author: + 62-721-781823, Fax: + 62-721-700682

  Biomass is still a primary energy source for cooking in developing countries. Currently, it is estimated that around 50% of the world's population (90% or about 3 billion people in developing countries) rely on biomass fuels (wood, dung and crop residues), which are typically burnt especially for cooking, heating, and lighting [1-2]. The use of biomass energy is environmentally benign if it is managed appropriately. In addition, carbon dioxide (CO

  , which were 390 μg/Nm

  3

  and 400 μg/Nm

  3

  , respectively. These numbers were higher than the national standards of 230 μg/Nm

  3

  for dust and 150 μg/Nm

  3

  for PM

  

10

.

  Keywords: Biomass, black carbon, gas emission, indoor cooking, in-kitchen air, opacity, particulate matter, stove.

  2

  . Wood stoves, however, resulted in high concentrations of dust and PM

  ) released during combustion of biomass, is finally utilized for photosynthesis during plant growth. If biomass was completely combusted, the use of biomass for cooking could be carbon dioxide-neutral [3]. Most biomass, however, is burned incompletely and produces other by-products which contribute to climate change. In the rural areas, wood fuel is used through direct, open combustion in a simple stove that results in incomplete combustion. Incomplete combustion processes can emit organic pollutants and fine particles. In effect, biomass combustion is related to significant pollutant emissions and hence, needs to be improved. Nussbaumer [4] stated that pollutant formation occurs in two ways: (1) Incomplete combustion that leads to high emissions of unburnt pollutants such as CO, soot, and PAH, and (2) fuel constituents such as N, K, Cl, Ca, Na, Mg, P, and S that form pollutants such as NO

  x and particles.

  Zhang and Smith (2003) noted that combustion of solid fuels in simple, poorly designed and maintained stoves contributed directly to low energy efficiency and, therefore, increased pressure on fuel resources [5]. Low combustion efficiency means that a large fraction of fuel carbon is converted to compounds other than carbon dioxide (CO

  2 ), i.e. products of incomplete combustion.

  These products mainly comprise CO and fine (inhalable) particles, and volatile as well as semi volatile organic compounds.

  In addition, people rarely erect a chimney to release flue gases resulting from biomass burning. This has resulted in dirty, unhealthy kitchens. Black carbon emitted during biomass burning accumulates and forms black soot on the walls and ceiling. Therefore, the use of biomass energy should be evaluated comprehensively.

  The relation of indoor air pollution and ill health condition has been well documented. For example, Bruce et al. (2002) highlighted that indoor air pollution may be attributed to some diseases including acute respiratory infections, chronic pulmonary disease, asthma, lung cancer, pulmonary tuberculosis, low birth weight and infant mortality, and cataracs [6].

  The aforementioned condition of wood fuel utilization applies to Indonesia. During the last ten years, biomass consumption in Indonesia was 272 million barrel oil equivalent [7] and most is used for cooking by rural and low income people. Most people burn wood fuel in open, simple woodstoves. Cooking is done in the kitchen without a chimney to release the flue gases. The by-products escape out of the building simply through windows, doors, porous walls and roofing. This condition caused black, dirty walls and ceiling in the kitchen.

  There are some studies on the woodstove energy efficiency in Indonesia. Nurhayati et al. [8], for example, reported that thermal efficiency of woodstoves used in brown sugar industries was around 15-18.6%, whereas the efficiency of traditional household and small restaurant woodstoves varied between 1.6% and 23.9%. Recently, Haryanto and Triyono [9] reported that thermal efficiency of woodstoves was 9-16%. Information on the emissions related to household stoves, however, is scarce. Therefore, investigations of emission characteristics resulting from fuel combustion for cooking are required. The results are expected to contribute in helping the design of efficient, low emission wood stoves. The objective of this research was to investigate in-kitchen air quality as related to different stoves used during cooking at Way Isem, a village in Lampung Province, Indonesia.

  2. Experimental

  2.1 Description of study site

  The experiment was conducted at Way Isem village in northern of Lampung Province. The village was located about 160 km (3 hours driving) from Bandar Lampung, the capital city of Lampung Province. Way Isem village has a population of 1,443 persons (739 male and 704 female) from 361 households. Most of the villagers are work farms. Rural homes in the field of

  10

  3

   

  , NO

  Journal of Sustainable Energy & Environment 2 (2011) 186 181-

Effect of Stove Types on In-kitchen Air Quality: Case Study at

Way Isem Village, Lampung Province, Indonesia

  U. Hasanudin 1,*

  

, A. Haryanto

  2 , J. Romero

  3

  1 Department of Agro-industrial Technology, Faculty of Agriculture, University of Lampung. Jl. Sumantri Brojonegoro No. 1, Bandar Lampung,

Indonesia, 35145. Email:

  2 Department of Agricultural Engineering, Faculty of Agriculture, University of Lampung. Jl. Sumantri Brojonegoro No. 1, Bandar Lampung,

Indonesia, 35145. Em

  3 Institute for Global Environmental Strategies, 2108-11 Kamiyamaguchi, Hayama, Kanagawa 240-0115, Japan. Email:

  

Abstract: The objective of this research was to investigate in-kitchen air quality as related to stove utilization during cooking. The

  experiment was conducted at Way Isem, a village located in the North of Lampung Province, Indonesia. Nine homes using four different fuels or stoves participated in this experiment with a total of fifteen samples - five wood stoves, five kerosene stoves, four liquefied petroleum gas (LPG) stoves and one biogas stove. In-kitchen air quality was measured using five parameters, namely SO

  2

  2

  , was also distinctly lower than the national standard of 400 μg/Nm

  , dust, PM

  10

  and opacity. In-kitchen air was sampled using a High Volume Air Sampler apparatus equipped with a vacuum pump. The air was then absorbed using a RAC 5 gas sampler for further analysis. Results showed that SO

  2

  content in the kitchen air for an hour of measurement ranged from 340 to 357 μg/Nm

  3

  , lower than the Indonesia standard of 900 μg/Nm

  3

  . NO

  2

  content, ranged from 12 to 19 μg/Nm

  3

1. Introduction

  Journal of Sustainable Energy & Environment 2 (2011) 181- 186

study were one-story houses with large backyards for gardening. the stove (Figure 1). A High Volume Air Sampler apparatus

  So far, no electricity grid is installed at the village. Because of (HiVol 3000 ECOTECH) equipped with a vacuum pump was relatively easy access to gather fire wood, energy consumption used to collect air samples for dust and PM determination for

  10

  for cooking is basically supplied by wood. The wood is gathered an hour. Particulate matter in the air sample was trapped in a from the yard or farm with no costs incurred . The wood is burnt membrane-type filter before air enters the inlet manifold. Particulate in a simple brick stove. For all households their kitchens were in analysis was performed based on the Indonesia National Standard

  

the back section of the house. Generally, the kitchens are designed (SNI) #19-7119.3-2005 released by the Bureau for National

for a wood stove without a chimney to release the flue gas. By- Standards (BSN, 2005a) [12].

products from fuel combustion were simply removed from the A RAC 5 Gas Sampler (New Star Environmental) capable

kitchen by natural ventilation through windows, doors, porous of testing five emission gases was used to measure NO and SO

  2

  2

  walls and roofs. This condition caused black, dirty walls and content at the same time. The RAC 5 Gas Sampler was equipped ceiling in the kitchen. with bubbler tubes to absorb the air. The sample air passes Some people with a better economic standing have through these tubes into 50 ml of reagent (absorbing solution) kerosene stoves. Smith et al. [10] clearly stated that the transition contained in each bubbler. The gas sampler arrangement is depicted of people away from reliance on wood as fuel toward commercial schematically in Figure 2. The scrubbed air was analyzed based (often fossil) fuels occurred due to people's living standard on the SNI standards #19-7119.2-2005 for NO and #19-7119.7-

  2 improvement. Through a kerosene conversion program, 20 villagers 2005 for SO [13-14].

  2

  recently (in 2010) also received an LPG stove from the government for free. The LPG and kerosene are purchased from Table 1. Sampling strategy for in-kitchen air quality measurement a local supplier for IDR.8000 (US$89 cent) per liter for kerosene (fifteen total samples). and IDR.15,500 (US$1.7) per bottle of 3-kg LPG. Sustaining the

  Woodstove LPG stove Kerosene stove Biogas stove

  use of LPG stoves was expensive or deemed as an unnecessary

  Home 1 √ √

  expense compared to using free and abundant wood as fuel so

  Home 2 √ √

  most of the people continued using wood as a primary fuel. In Home 3

  √

  fact most kerosene and LPG stoves were kept in a drawer due to Home 4

  √ √ √ Home 5

  the high price of kerosene and many accidents involving LPG √ √

  stoves being reported in the media. Therefore, the people

  Home 6 √ √

  continued running their wood stoves as a primary stove.

  Home 7 √

  Home 8 √

  In 2007, Way Isem village became a recipient of the Self

  Home 9 √

  Sufficient Energy Village (SSEV) pilot project. The project scheme is for the village to grow Jatropha curcas as a source of energy with assistance from a foundation. The jatropha plant was able to produce seeds within six months after planting (the seedling was planted in a plastic bag for one month). The seeds from the harvested ripe jatropha fruits were processed to produce biokerosene, i.e. crude jatropha oil (CJO). All the facilities, including seed, were provided from the sponsor. The CJO needs to be further

  HiVol 3000 processed so that it can be used to run a generator and produce electricity. The jatropha seed supply, however, was not sufficient due to low yields. Production was intermittent so the CJO was merely sold through the sponsor. In order to attract people into participating in the program, the sponsor also provided biogas digesters to generate biogas fuel from jatropha cake. In fact, 20

  Stove families have already received biogas digester through the SSEV program, but only one was in operation when the experiment took place. The people showed high enthusiasm for the biogas digester

  RAC 5 Gas because it is a cleaner source of cooking fuel compared to wood Sa mpler and it is almost free compared to the LPG. However, with the low technology transfer and limited training capacity, the villagers did not have the skills to fix even small problems such as gas holder leaks. But the main problem was that the economic benefits from jatropha cultivation was not attractive when compared to planting other crops such as cassava so the supply of jatropha Figure 1. Field measurement to evaluate in-kitchen air quality. cake used in the biogas digester was not readily available [11].

2.2 Experimental settings

  Nine houses using four different fuel/stove participated in this experiment making taking a total of fifteen samples, which included five cordwood stoves, five kerosene stoves, four LPG stoves and one biogas stove (see Table 1). As stated earlier, it was hard to find people using kerosene, LPG and biogas stoves. In cases that a home had more than one stove the emission measurement were made separately for each stove on a different day. This strategy was adopted to avoid the effect of previous conditions created by a different fuel. Data recorded included the kitchen condition, and stove and fuel types. Measurements of air

  A. Fritted tube

  B. Absorbing solution

  C. Mist trap

  D. Flow meter

  E. Control valve

  F. Pump

  quality were conducted in the kitchen at a point 2-3 meters from Figure 2. Sketch for gas sampler arrangement.

   

3.1 SO 2 emission

  35.7 4 10.3

  62.1 AVG 371.02

  13.1 4 96.0 18.8 90.93 5 840.9

  57.9

  53.8 3 61.0

  98.7

  11.38 Ash 1 589.0 217.4 193.9 31.9 2 268.2

  7.39

  15.98 19.20 11.4 400 SD 4.88

  10.9 AVG 17.58

  16.0 5 15.8

  12.1

  28.1

  76.12

  9.6 3 22.1

  10.8

  18.0 15.5 11.4 2 21.9

  2 emission 1 17.8

  13.84 NO

  9.93

  AVG 356.6 342.98 340.35 340.1 900 SD 8.56

  2 359.6 350.7 324.4 3 349.3 341.8 334.6 4 363.7 355.0 346.1 5 345.8 330.8

  2 emission 1 364.6 336.6 356.3 340.1

  Home # Wood Stove Kerosene Stove LPG Stove Biogas Stove Indonesia Standard SO

  Table 2. Emission data resulted from the experiment.

  90.98 87.93 31.9 230 SD 335.64

  10 1 866.6 89.9 92.4 66.6 2 215.4

  77.47 PM

  3 4 8

  = − ₁ ² ) (

  X ⁿ _{i i} ∑

  X X

  0.58 Note: Standard deviation (SD) is defined as SD =

  0.55

  35 SD 0.89

  4

  3.5

  5.4

  4 5 10

  5

  6

  2 emissions will not be different due to the different fuels used.

  4 3 10

  5

  22.10 Opacity 1 10 6 3 4 2 9

  13.47

  65.98 67.83 66.6 115 SD 299.61

  57.9 AVG 405.46

  53.8 5 321.8

  59.1

  80.0 4 104.7

  62.3

  45.1 3 518.8

  60.7

  The small discrepancy may be due to the quality of combustion.

  emissions in this study mostly resulted from atmospheric nitrogen and therefore, NO

  Journal of Sustainable Energy & Environment 2 (2011) 186 181-

  3

  than that of biomass [18]. In fact, the combustion of fossil fuel has been claimed to be the major anthropogenic source of SO

  2

  ) emissions from the stoves directly related to the sulphur content of fuels used [17]. It is well known that the combustion of fossil fuels produce more SO

  x

  The sulfur oxides (SO

  2 levels.

  but cordwood stoves, on the other hand, produced slightly higher SO

  2

  concentrations found during cooking activities was well below the required national standard for ambient air regardless of stove type. It can also be seen from Figure 3 that kerosene, LPG, and biogas stoves produced a relatively comparable amount of SO

  2

  . Therefore, SO

  content for an hour must not exceed 900 μg/Nm

  Our data, however, showed that biomass combustion produce higher SO

  2

  (for wood stove). Standard ambient air quality for Indonesia, as found in the Government Regulation No. 41/1999 [16], requires that SO

  3

  (for biogas stove) to 356.6 μg/Nm

  3

  concentration was in the range of 340.1 μg/Nm

  2

  content in-kitchen air in relation to different types of stove. The SO

  2

  Figure 3 shows the SO

  3. Results and Discussion Table 2 shows the emission data resulted from the experiment.

  Fuel combustion produces smoke at different intensities due to different moisture content and different size, form and color of the particulates. The opacity was measured using the Ringelmann scale and was presented as a percentage of the standard background. The method was detailed in the SNI standard # 19-7117.11-2005 [15].

  2 emissions.

  2

  2

  The NO

  than those of gas or kerosene stoves [4]. Our results, however, showed a different tendency. These implied that NO

  2

  emissions and the nitrogen content of the fuel. Nussbaumer (2003) confirmed that biomass furnaces exhibit relatively high emissions of NO

  2

  emission levels will depend on the combustion temperature and the fuel composition as well. Dinca et al. [19] noted the correlation between the NO

  2

  from the fixation of atmospheric nitrogen in the combustion process. Therefore, NO

  2

  from the conversion of chemically bound nitrogen in the fuel, and (2) formation of NO

  2

  formation may occur by two different mechanisms: (1) formation of NO

  2

  3 .

  . This may be due to the low efficiency of the woodstoves used in this experiment as reported recently by Haryanto and Triyono [9].

  μg/Nm

  in average for the LPG stove. Again, these quantities were much lower than the national standard of 400

  3

  for the biogas stove to 19.2 μg/Nm

  3

  emissions from all stoves were basically comparable in the window of 11.4 μg/Nm

  2

  content in the kitchen air as related to different types of stove is presented in Figure 4. It was observed that NO

  2

  The NO

  2 emission

  3.2 NO

5 AVG 9.4

  Journal of Sustainable Energy & Environment 2 (2011) 186 181-

  , on the other hand, remain in the atmosphere for shorter periods. The importance of PM

  300 310 320 330 340 350 360 370

  Cordwood Kerosene LPG Biogas SO ² (μ g/ N m ³ )

  Stove  Type Figure 3. SO

  2

  content in-kitchen air quality as related to different types of stove.

  Figure 7 revealed the percentage of opacity in the kitchens studied. The opacity of kitchen air met the national standard of 35% maximum [25]. The figure clearly shows that wood stoves resulted in higher air opacity than the other three stoves did. The opacity is caused by smoke which is a sign of

  3.4 Smoke opacity

  is that it can penetrate deeply into the respiratory tract and cause respiratory illnesses in humans. It is important, therefore, to develop improved wood- burning stoves in order to increase the efficiency and reduce particle emissions.

  10

  3.3 Particulate emission Figures 5 and 6 respectively showed the concentration of dust and particulate matter with a diameter of 10

  , respectively. The type of stove used as well as the type of wood and its moisture content were likely be substantial variables. The other three stoves (kerosene, LPG, and biogas) produced dust and PM

  10

  remains in the atmosphere for longer periods because of its low settling velocity. Particulates greater than PM

  10

  is the major component of dust polluting the air in the kitchen. The reason for this phenomenon is that PM

  10

  emissions were comparable with dust emissions for each type of stove. This implies that PM

  10

  Our results indicated higher PM levels for households using biomass stoves compared with those using cleaner fuels. These findings imply that biomass burning for cooking contributes substantially to indoor particulate levels. The results concurred with previous work. Jiang and Bell reported that urban households using cleaner fuels (such as natural gas), had significantly lower indoor PM levels than did rural households using biomass [20]. In Tamil Nadu, India, cooks using biomass fuels also experienced higher indoor PM4 levels than cooks using clean fuels such as kerosene or gas did [21]. Smith et al. [22] concluded emissions of by-products from incomplete combustion decrease

  from unprocessed biomass to processed biomass (charcoal) to liquid fuels to gaseous fuels. Although our results are limited by

  10 emissions lower than the national standards.

  10

  It can also be observed from Figure 5 and 6 that PM

  3

  μm or less (PM

  10

  ) in the kitchen air. Both figures demonstrated that particulate emissions from biomass combustion was much higher than those of the other three stoves. Jiang and Bell [20] reported that indoor particle levels may be attributed to different fuel types

  and kitchen designs. Dust levels in kitchen air in relation to liquid

  and gas fuels varied from 31.9 μg/Nm

  3

  with biogas stoves to 91 μg/Nm

  3

  with kerosene stoves. Wood stoves, however, resulted in a dust content of 371 μg/Nm

  on average. A similar trend was observed for PM

  for dust and PM

  10

  levels, which were in the range of 66 to 68 μg/Nm

  3

  with kerosene, LPG, and biogas stoves; whilst woodstoves resulted in 405.5 μg/Nm

  3

  on average. Dust and PM

  10

  levels showed that particle emissions from wood stoves were above the national standard of 230 and 115

  μg/Nm

  3

  the small sample size, these findings confirmed the growing body of evidence that biomass fuels can result in high indoor air pollution levels, which in turn can contribute to ill health such as respiratory infections, [23] and decreasing of lung function [24].

35 Cordwood Kerosene LPG Biogas

  3 ) Stope  Types Figure 5. Dust content in the kitchen air as related to different types of stove.

  Cordwood Kerosene LPG Biogas PM ¹⁰ (μ g /N m ³ )

  Figure 7. Opacity of in-kitchen air as related to different types of stove.

  12 Cordwood Kerosene LPG Biogas Op a ci ty  (% ) Stove  Types

  10

  8

  6

  4

  2

  content in the kitchen air as related to different types of stove.

  10

  Stove  Types Figure 6. PM

  100 200 300 400 500 600 700 800

  Cordwood Kerosene LPG Biogas Du st (μ g/ N m

  5

  10

  15

  20

  25

  NO ² (μ g/ N m ³ )

  Stove Types Figure 4. NO

  2

  content in the kitchen air as related to different types of stove

  100 200 300 400 500 600 700 800

  30

   

  Regulation No. 41/1999 on the Controlling Air Pollutant (1999).

  Workshop “Biomass as Sustainable Energy.” Agency for The Assessment and Application of Technology (BPPT), Jakarta, November 29 – December 1, 2010.

  [12] BSN (Bureau for National Standard), SNI # 19-7119.2-

  2005 Ambient Air – Part 2: Test code for nitrogen dioxide (NO

  2 ) content with Griess Saltzman metode using spectrophotometry (in Bahasa Indonesia) .

  [13] BSN (Bureau for National Standard), SNI # 19-7119.3-

  2005 Ambient Air – Part 3: Test code for total suspended with high volume air sampler (HVAS) instrument using gravimetry (in Bahasa Indonesia).

  [14] BSN (Bureau for National Standard), SNI # 19-7119.7-

  2005 Ambient Air – Part 7: Test code for sulphur dioxide (SO 2 ) content with pararosaniline metode using spectrophotometry (in Bahasa Indonesia).

  [15] BSN (Bureau for National Standard), SNI # 19-7117.11-

  2005 Fluegas Emission from Static Source – Part 11: Test code for air opacity using Ringelmann scale for black smoke (in Bahasa Indonesia) .

  [16] President of the Republic of Indonesia, Government

  [17] Khodier A, Nigel S, Kilgallon P, Legrave N, Investigation of gaseous emissions and ash deposition in a pilot-scale PF combustor co-firing cereal co-product biomass with coal,

  Makes People Cook with Improved Stoves? A Comparative Review, joint ESMAP/UNDP report (1992). [11] Hasanudin U, Haryanto A, Sustainability assessment of

  International Conference on Renewable Energies and Power Quality (ICREPQ’10) (2010) Granada (Spain), 23 rd

  to 25

  th March, 2010.

  [18] Erisman JW, Acid Deposition and Energy Use, Encyclopedia of Energy 1 (2004) 1-15, Elsevier, Amsterdam. [19] Dinca C, Badea A, Marculescu C, Gheorghe C, Environmental analysis of biomass combustion process, Proceedings of

  the 3rd WSEAS Int. Conf. on Renewable Energy Sources

  (2009) 234-238, University of La Laguna, Tenerife, Canary Islands, Spain, July 1-3, 2009. [20] Jiang R, Bell ML, A Comparison of Particulate Matter from Biomass-Burning Rural and Non-Biomass-Burning

  Urban Households in Northeastern China, Environmental

  Health Perspectives 116 (2008) 907-914.

  [21] Balakrishnan K, Sankar S, Parikh J, Padmavathi R, Srividya K, Venugopal V, Prasad S, Pandey VL, Daily average exposures to respirable particulate matter from combustion of biomass fuels in rural households of southern India, Environmental Health Perspectives 110 (2002) 1069-1075.

  [22] Smith KR, Khalil MAK, Rasmussen RA, Thorneloe SA, Manegdeg F, Apte M, Greenhouse gases from biomass and fossil fuel stoves in developing countries: A manila pilot study, Chemosphere 26 (1993) 479-505

  [23] Ezzati M, Kammen DM, Quantifying the Effects of Exposure to Indoor Air Pollution from Biomass Combustion on Acute Respiratory Infections in Developing Countries,

  Environ Health Perspect 109 (2001) 481-488.

  biomass utilization for energy, case study in Lampung, Indonesia (2010) Presentation at 7th Biomass-Asia

  Technology Seminar, University of Lampung, October 18- 19, 2010. [10] Smith KR, van der Plas D, Barnes F, Openshaw K, What

  Journal of Sustainable Energy & Environment 2 (2011) 186 181-

  household stoves (in Bahasa Indonesia) (2010) Sains and

  [8] Nurhayati T, Waridi Y, Roliadi H, Progress in the technology of energy conversion from woody biomass in Indonesia, For. Stud. China 8 (2006) 1-8. [9] Haryanto A, Triyono S, Energetic characteristic of

  incomplete combustion. This means that woodstoves produced more smoke as compared to liquid or gas stoves. Smith et al. [26] pointed out that simple stoves using solid fuels do not merely convert fuel carbon into carbon dioxide. Such stoves actually convert a significant portion of the fuel carbon into products of incomplete combustion. In this case, local practices, the type of stove, as well as the wood species and moisture content, are important variables.

  The significance of smoke particles is that they are composed of 50-60% organic carbon and 5-10% black carbon. Without a chimney or exhaust fan, smoke is the source of the black soot accumulated on the walls and ceiling of the kitchens. Smith et al. (2005) firmly stated that indoor smoke from solid fuel combustion is the second-leading environmental risk factor contributing to the total burden of disease in India, and the third- largest risk factor overall [27].

4. Conclusion

  indoor air pollution exposure in developing countries

  μg/Nm

  Handbook of Energy and Economic Statistics of Indonesia (2007) Accsesed f (May 01, 2008).

  [7] MEMR (Ministry of Energy and Mineral Resources),

  Our experiment concluded that opacity, NO

  2 and SO

  2 concentrations in kitchen air as related to the type of fuel or stoves used for cooking was far below the national standard, regardless fuel and stoves type. Biomass combustion results in

  elevated a ir pollution, especially particulate matter. The dust

  and PM10 concentrations during cooking time due to wood stove was 371 and 405

  μg/Nm

  3 , respectively. These numbers were higher than the national standards of 230 and 115

  3 for dust and PM10, respectively.

  [5] Zhang JJ, Smith KR, Indoor air pollution: A global health concern, British Medical Bulletin 68 (2003) 209-225. [6] Bruce N, Perez-Padilla R, Albalak R, The health effects of

  Further field studies are necessary to evaluate the use of improved stoves and to quantify the carbon savings from the use of specific stoves.

  Acknowledgment

  (2002) World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland.

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